GS116 - are all ports equal?

I have recently had a few issues in my home network and have checked all the structured cabling.  All is now ok.  In doing so, I noticed that out of the 16 ports on my GS116, ports 1-4 seemed to get better speed of throughput than the others.  When our BB was only 50Mb/s this was not noticeable, but now I have FTTP at 500Mb/s, it is clearly an issue as some ports get much less throughput.

The GS116 is a full 32Gb/s switch, by which all ports SHOULD be able to run bi-directional 1Gb/s.  Clearly the BB router throttles to 500Mb/s, but why is there this apparent prioritisation by the port number on the Netgear switch?  Is this to do with the internal architecture?  Or is this a possible fault?

Thanks for any advice.

Andy